Electrical Issues on my 1987

hey everyone I am new to this forum and I am not that experienced with the old gmc trucks, I have a 1987 gmc sierra 1500 4x4 305 tbi th350 tranny. I am just trying to fix it up and make it my daily driver. I recently put a new turbo 350 tranny in it since the other one **** the bed on me. I got the tranny in and now the truck wont start. I charged the battery up and made sure there was a charge. I have power to my stereo but there are no headlights or power when I turn over the key. The seat belt and brake light come on when I turn it on and try to start it. I tried toughing a screw driver to the starter to see if there was power going to the solenoid and it turns over that way. If you try to boost it with another car it doesn't turn over not even a noise out of it. I am completely stuck. I checked all the fuses they seemed fine. the only thing I saw but wasn't sure of was the ignition fuse in the fuse panel. there is the normal fuse like a 20A fuse in there but then there is another spot for a ignition fuse that would be like a square one maybe. I could be wrong. Also I changed out the ignition switch today thought maybe that would help, it did nothing. Any help would be great. Thank you everybody.

Welcome to the club, it's great to have you aboard. I would have the battery load tested, then have the starter checked and of course check all connections good. Good luck with your project man. :glasses:

Try looking into the neutral safety switch circuit. This is the circuit that won't allow the car to start if the transmission is not in Park or Neutral. I had a Dodge minivan that had the neutral safety switch connector on the transmission housing. The circuit connector backed out of the the connection on the tranny housing just enough to break the circuit and my van wouldn't start. Right when I was leaving for work, too! Took me half the next day to figure out what was going on and track it down. But some of the other symptoms I had were similar to yours. The lights would come on, and when I would turn the key the radio and dash lights would go out like it was preparing for the engine to crank, only it didn't. When I bypassed the circuit and jumped the starter directly, the van started.

Check all your connection for the Neutral safety switch circuit, and then check all the fuses and relays for the same circuit.